U.S. patent number 7,197,273 [Application Number 10/918,989] was granted by the patent office on 2007-03-27 for sheet feeding apparatus, image reading apparatus, and image forming apparatus.
This patent grant is currently assigned to Sharp Kabushiki Kaisha. Invention is credited to Shuhji Fujii, Takashi Imai, Kaoru Ishikura.
United States Patent |
7,197,273 |
Imai , et al. |
March 27, 2007 |
Sheet feeding apparatus, image reading apparatus, and image forming
apparatus
Abstract
In a sheet feeding apparatus, a contact-type sensor for
detecting sheet-like documents stored in document tray is separated
into upper document detector and a lower document detector arranged
at upper and lower sides of the document tray, respectively. The
sheet-like documents are detected separately with two actuators of
the corresponding detectors. Accordingly, the requirement of a
prior art for having a contact of the sensor increased in length in
order to detect the sheets from a maximum to zero in the sheet
storing unit can be eliminated.
Inventors: |
Imai; Takashi (Nara,
JP), Fujii; Shuhji (Kyoto, JP), Ishikura;
Kaoru (Kyoto, JP) |
Assignee: |
Sharp Kabushiki Kaisha (Osaka,
JP)
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Family
ID: |
34191049 |
Appl.
No.: |
10/918,989 |
Filed: |
August 16, 2004 |
Prior Publication Data
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Document
Identifier |
Publication Date |
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US 20050042005 A1 |
Feb 24, 2005 |
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Foreign Application Priority Data
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Aug 18, 2003 [JP] |
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2003-294592 |
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Current U.S.
Class: |
399/371;
399/367 |
Current CPC
Class: |
G03G
15/6564 (20130101); G03G 15/6567 (20130101) |
Current International
Class: |
G03G
15/00 (20060101) |
Field of
Search: |
;271/265.01,265.02,153,145,265,126,127,11 ;400/624
;399/23,369-371,376,377,367 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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05-094063 |
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Apr 1993 |
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JP |
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07-301962 |
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Nov 1995 |
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JP |
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11-199065 |
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Jul 1999 |
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JP |
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2001-002286 |
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Sep 2001 |
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JP |
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Primary Examiner: Nguyen; Anthony H
Attorney, Agent or Firm: Renner, Otto, Boisselle &
Sklar, LLP
Claims
The invention claimed is:
1. A sheet feeding apparatus comprising: a sheet storing unit in
which a number of sheets are stored in a stack; a sheet feeding
mechanism for picking up and feeding out the sheets stored in said
sheet storing unit in a sequence from the uppermost one; and a
sheet detector having a contact for contacting the sheets stored in
said sheet storing unit to detect whether the sheets are stored or
not in said sheet storing unit, wherein said contact consists of a
first contact extending downwardly from a higher position than said
sheet storing unit and a second contact extending upwardly from a
lower position than said sheet storing unit, said sheet detector
includes a first sheet detector arranged at a position higher than
said sheet storing unit and a second sheet detector arranged at a
position lower than said sheet storing unit, said first contact is
provided in said first sheet detector while said second contact is
provided in said second sheet detector, and said first and second
contacts are configured so that a first detecting area of said
first contact for detecting the sheets stored in said sheet storing
unit, and a second detecting area of said second contact for
detecting the sheets stored in said sheet storing unit partially
overlap each other.
2. The sheet feeding apparatus as set forth in claim 1, further
comprising: a height detector for detecting the height of the
uppermost one of the sheets stored in said sheet storing unit; an
elevation/lowering mechanism for elevating or lowering said sheet
storing unit at a predetermined speed within a predetermined range;
and a control circuit for controlling said elevation/lowering
mechanism in response to a detection result of said height detector
so as to keep the height of said sheet storing unit where the
height of the uppermost one of the sheets stored in said sheet
storing unit is equal to a height for picking up the sheets within
said first and second detecting areas.
3. The sheet feeding apparatus as set forth in claim 2, further
comprising: a sheet volume calculating circuit for determining a
volume of the sheets stored in said sheet storing unit based on a
detection result of said first contact and a detection result of
said second contact.
4. The sheet feeding apparatus as set forth in claim 3, further
comprising: a sheet storing unit position detector for detecting
whether or not said sheet storing unit is at its lower-limit
position within said predetermined range; and a control circuit for
controlling said elevation/lowering mechanism to elevate said sheet
storing unit at a speed higher than said predetermined speed when
said sheet storing unit position detector detects that said sheet
storing unit is at the lower-limit position and said sheet volume
calculating circuit determines that the volume of the sheets stored
in said sheet storing unit is the volume which is not detected
within said first detecting area.
5. An image reading apparatus which has a sheet feeding apparatus
comprising: a sheet storing unit in which a number of sheets are
stored in a stack; a sheet feeding mechanism for picking up and
feeding out the sheets stored in said sheet storing unit in a
sequence from the uppermost one; and a sheet detector having a
contact for contacting the sheets stored in said sheet storing unit
to detect whether the sheets are stored or not in said sheet
storing unit, wherein said contact consists of a first contact
extending downwardly from a higher position than said sheet storing
unit and a second contact extending upwardly from a lower position
than said sheet storing unit, said sheet detector includes a first
sheet detector arranged at a position higher than said sheet
storing unit and a second sheet detector arranged at a position
lower than said sheet storing unit, said first contact is provided
in said first sheet detector while said second contact is provided
in said second sheet detector, and said first and second contacts
are configured so that a first detecting area of said first contact
for detecting the sheets stored in said sheet storing unit, and a
second detecting area of said second contact for detecting the
sheets stored in said sheet storing unit partially overlap each
other.
6. The image reading apparatus as set forth in claim 5, wherein
said sheet feeding apparatus further comprising: a height detector
for detecting the height of the uppermost one of the sheets stored
in said sheet storing unit; an elevation/lowering mechanism for
elevating or lowering said sheet storing unit at a predetermined
speed within a predetermined range; and a control circuit for
controlling said elevation/lowering mechanism in response to a
detection result of said height detector so as to keep the height
of said sheet storing unit where the height of the uppermost one of
the sheets stored in said sheet storing unit is equal to a height
for picking up the sheets within said first and second detecting
areas.
7. The image reading apparatus as set forth in claim 6, wherein
said sheet feeding apparatus further comprising: a sheet volume
calculating circuit for determining a volume of the sheets stored
in said sheet storing unit based on a detection result of said
first contact and a detection result of said second contact.
8. The image reading apparatus as set forth in claim 7, wherein
said sheet feeding apparatus further comprising: a sheet storing
unit position detector for detecting whether or not said sheet
storing unit is at its lower-limit position within said
predetermined range; and a control circuit for controlling said
elevation/lowering mechanism to elevate said sheet storing unit at
a speed higher than said predetermined speed when said sheet
storing unit position detector detects that said sheet storing unit
is at the lower-limit position and said sheet volume calculating
circuit determines that the volume of the sheets stored in said
sheet storing unit is the volume which is not detected within said
first detecting area.
9. An image forming apparatus which has a sheet feeding apparatus
comprising: a sheet storing unit in which a number of sheets are
stored in a stack; a sheet feeding mechanism for picking up and
feeding out the sheets stored in said sheet storing unit in a
sequence from the uppermost one; and a sheet detector having a
contact for contacting the sheets stored in said sheet storing unit
to detect whether the sheets are stored or not in said sheet
storing unit, wherein said contact consists of a first contact
extending downwardly from a higher position than said sheet storing
unit and a second contact extending upwardly from a lower position
than said sheet storing unit, said sheet detector includes a first
sheet detector arranaed at a position higher than said sheet
storing unit and a second sheet detector arranged at a position
lower than said sheet storing unit, said first contact is provided
in said first sheet detector while said second contact is provided
in said second sheet detector, and said first and second contacts
are configured so that a first detecting area of said first contact
for detecting the sheets stored in said sheet storing unit, and a
second detecting area of said second contact for detecting the
sheets stored in said sheet storing unit partially overlap each
other.
10. The image forming apparatus as set forth in claim 9, wherein
said sheet feeding apparatus further comprising: a height detector
for detecting the height of the uppermost one of the sheets stored
in said sheet storing unit; an elevation/lowering mechanism for
elevating or lowering said sheet storing unit at a predetermined
speed within a predetermined range; and a control circuit for
controlling said elevation/lowering mechanism in response to a
detection result of said height detector so as to keep the height
of said sheet storing unit where the height of the uppermost one of
the sheets stored in said sheet storing unit is equal to a height
for picking up the sheets within said first and second detecting
areas.
11. The image forming apparatus as set forth in claim 10, wherein
said sheet feeding apparatus further comprising: a sheet volume
calculating circuit for determining a volume of the sheets stored
in said sheet storing unit based on a detection result of said
first contact and a detection result of said second contact.
12. The image forming apparatus as set forth in claim 11, wherein
said sheet feeding apparatus further comprising: a sheet storing
unit position detector for detecting whether or not said sheet
storing unit is at its lower-limit position within said
predetermined range; and a control circuit for controlling said
elevation/lowering mechanism to elevate said sheet storing unit at
a speed higher than said predetermined speed when said sheet
storing unit position detector detects that said sheet storing unit
is at the lower-limit position and said sheet volume calculating
circuit determines that the volume of the sheets stored in said
sheet storing unit is the volume which is not detected within said
first detecting area.
13. An image forming apparatus comprising: an image reading
apparatus in which a sheet feeding apparatus is incorporated, said
sheet feeding apparatus comprising: a sheet storing unit in which a
number of sheets are stored in a stack; a sheet feeding mechanism
for picking up and feeding out the sheets stored in said sheet
storing unit in a sequence from the uppermost one; and a sheet
detector having a contact for contacting the sheets stored in said
sheet storing unit to detect whether the sheets are stored or not
in said sheet storing unit, wherein said contact consists of a
first contact extending downwardly from a higher position than said
sheet storing unit and a second contact extending upwardly from a
lower position than said sheet storing unit, said sheet detector
includes a first sheet detector arranged at a position higher than
said sheet storing unit and a second sheet detector arranged at a
position lower than said sheet storing unit, said first contact is
provided in said first sheet detector while said second contact is
provided in said second sheet detector, and said first and second
contacts are configured so that a first detecting area of said
first contact for detecting the sheets stored in said sheet storing
unit, and a second detecting area of said second contact for
detecting the sheets stored in said sheet storing unit partially
overlap each other.
14. The image forming apparatus as set forth in claim 13, wherein
said sheet feeding apparatus further comprising: a height detector
for detecting the height of the uppermost one of the sheets stored
in said sheet storing unit; an elevation/lowering mechanism for
elevating or lowering said sheet storing unit at a predetermined
speed within a predetermined range; and a control circuit for
controlling said elevation/lowering mechanism in response to a
detection result of said height detector so as to keep the height
of said sheet storing unit where the height of the uppermost one of
the sheets stored in said sheet storing unit is equal to a height
for picking up the sheets within said first and second detecting
areas.
15. The image forming apparatus as set forth in claim 14, wherein
said sheet feeding apparatus further comprising: a sheet volume
calculating circuit for determining a volume of the sheets stored
in said sheet storing unit based on a detection result of said
first contact and a detection result of said second contact.
16. The image forming apparatus as set forth in claim 15, wherein
said sheet feeding apparatus further comprising: a sheet storing
unit position detector for detecting whether or not said sheet
storing unit is at its lower-limit position within said
predetermined range; and a control circuit for controlling said
elevation/lowering mechanism to elevate said sheet storing unit at
a speed higher than said predetermined speed when said sheet
storing unit position detector detects that said sheet storing unit
is at the lower-limit position and said sheet volume calculating
circuit determines that the volume of the sheets stored in said
sheet storing unit is the volume which is not detected within said
first detecting area.
17. An image forming apparatus comprising: an image reading
apparatus in which a sheet feeding apparatus is incorporated, said
sheet feeding apparatus comprising: a sheet storing unit in which a
number of sheets are stored in a stack; a sheet feeding mechanism
for picking up and feeding out the sheets stored in said sheet
storing unit in a sequence from the uppermost one; and a sheet
detector having a contact for contacting the sheets stored in said
sheet storing unit to detect the presence or absence of the sheets;
wherein said contact consists of a first contact extending
downwardly from a higher position than said sheet storing unit and
a second contact extending upwardly from a lower position than said
sheet storing unit; said sheet detector includes a first sheet
detector arranged at a position higher than said sheet storing unit
and a second sheet detector arranged at a position lower than said
sheet storing unit, and said first contact is provided in said
first sheet detector while said second contact is provided in said
second sheet detector; and said first and second contacts are
configured so that a first detecting area of said first contact for
detecting the sheets stored in said sheet storing unit and a second
detecting area of said second contact for detecting the sheets
stored in said sheet storing unit partially overlap each other; a
height detector for detecting the height of the uppermost one of
the sheets stored in said sheet storing unit; an elevation/lowering
mechanism for elevating or lowering said sheet storing unit at a
predetermined speed within a predetermined range; a control circuit
for controlling said elevation/lowering mechanism in response to a
detection result of said height detector so as to keep the height
of said sheet storing unit where the height of the uppermost one of
the sheets stored in said sheet storing unit is equal to a height
for picking up the sheets within said first and second detecting
areas; a sheet volume calculating circuit for determining a volume
of the sheets stored in said sheet storing unit based on a
detection result of said first contact and a detection result of
said second contact; a memory unit for storing the data of images
read by said image reading apparatus and inputted from the
external; an image forming unit for forming images based on the
data stored in said memory unit; and a control circuit for setting
an allocated capacity of said memory unit for storing the data of
images read by said image reading apparatus in response to the
volume of the sheets stored in said sheet storing unit calculated
by said sheet volume calculating circuit, and for permitting the
input of images from the external when the allocated capacity of
said memory unit for storing the data of images read by said image
reading apparatus is not larger than a predetermined value.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
This non-provisional application claims priority under 35 U.S.C.
.sctn.119(a) on Patent Application No. 2003-294592 filed in Japan
on Aug. 18, 2003, the entire contents of which are hereby
incorporated by reference.
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a sheet feeding apparatus for
reading image of sheet-like document by feeding from a document
tray (a sheet storing unit) a series of sheets, each on which image
of document is formed, to read the image of document formed on the
sheet, and also relates to an image reading apparatus and an image
forming apparatus, each equipped with the sheet feeding
apparatus.
2. Description of Related Art
It is commonly known that an up-to-date image forming apparatus or
the like is equipped with a document reading apparatus where a
series of sheets each having image of document formed thereon are
set by being stacked and stored in a document tray are
automatically transferred sheet by sheet from the document tray to
an image reading apparatus for sequentially reading the image of
document formed on the sheet. The image forming apparatus equipped
with such a document reading apparatus is designed to read a
document and form an image at high efficiency. It is also demanded
to read an image from a document, convert the read result into an
electronic data, and form an image of the document from the
electronic data obtained as described above at higher speeds (See
Japanese Patent Application Laid-Open No. H05-94063A (1993) and
Japanese Patent Application Laid-Open No. H07-301962A (1995),
etc).
So far for high-speed processing of the sheet-like documents, the
number of sheet-like documents stored in the document tray in a
conventional document reading apparatus is substantially 100 to
200. Also, as the document reading apparatus has been improved and
advanced at its sheet feeding unit, the types of documents to be
conveyed are increased.
It is essential in the document reading apparatus permitting a
series of sheets on which image of documents are formed to be set
(stored) in the document tray and fed out in a sequence for reading
the image of the document with an image reading apparatus to take
out (pick up) the uppermost one of the sheets stacked in the
document tray before feeding to the image reading apparatus. For
the purpose, the document tray is used of a lift type tray
(elevation/lowering tray) having a sheet elevation/lowering
function (in upward and downward directions) (See Japanese Patent
Application Laid-Open No. H11-199065A (1999)). Such an
elevation/lowering tray has a sheet detector (a document detector)
for detecting whether or not the sheets are correctly set in the
elevation/lowering tray particularly throughout the
elevation/lowering range of the elevation/lowering tray. When so,
it is also detected whether the sheets are placed at their correct
position at the deepest end of the elevation/lowering tray.
Such sheet detectors are employed as contact type sensors at the
upper side or the lower side in either a common fixed type tray or
an elevation/lowering tray of the document tray. The sheet detector
has a bar-like contact thereof provided to come into contact with
the leading end of the sheets so as to detect whether the sheets
are correctly set or not.
However, when the number of sheets set in the document tray becomes
larger, the contact of the sensor has to be increased in the
overall length as shown in FIG. 1 and FIG. 2. More particularly,
when a sensor S1' is provided at the upper side of a document tray
22, the contact S1a' of the sensor S1' has to be increased in the
area of the movement, that is, it is simply required to increase
the length of the contact S1a'. This may cause interruption between
the contact S1a' and a guide-in roller R1, between the contact S1a'
and a pair of separate rollers R2 and R2a, and between the contact
S1a' and the axis of each roller. Also, as shown in FIG. 2, when a
sensor S1 is provided at the lower side of the document tray 22,
the movement area of its contact S1a may relatively be small.
However, when there is a curled sheet SR and the number of the
sheets in the stack SB is decreased, the detection of the sheets in
the state where document tray 22 elevates may be difficult thus
resulting in fault detection. Moreover, when the sensor located at
the upper side of the document tray, not shown, and the number of
sheets becomes smaller, a curled sheet may hardly be detected.
On the other hand, an optical sensor is used for projecting light
onto the sheets from the upper side to the lower side or from the
lower side to the upper side to detect the sheets in the document
tray. However, such an optical sensor used as the sheet detector
requires a troublesome adjustment for detecting the sheets from one
type to another. In addition, its detecting operation is hardly
applicable to not only transparent OHP sheets but also
semi-transparent sheets or transparent portion contained
sheets.
BRIEF SUMMARY OF THE INVENTION
The present invention has devised in view of the foregoing
drawbacks and its object is to provide a sheet feeding apparatus in
which the contact of a contact-type sheet detector is separated
into two parts provided at both upper and lower sides of a document
tray, respectively whereby the foregoing drawbacks can be
eliminated and a variety of control operations which are not
conducted by any conventional detector can be carried out. It is
also another object of the present invention to provide an image
reading apparatus equipped with such sheet feeding apparatus and an
image forming apparatus equipped with such image reading
apparatus.
A sheet feeding apparatus as a first aspect of the present
invention is a sheet feeding apparatus comprising: a sheet storing
unit in which a number of sheets are stored in a stack; a sheet
feeding mechanism for picking up and feeding out the sheets stored
in the sheet storing unit in a sequence from the uppermost one; and
a sheet detector having a contact for contacting the sheets stored
in the sheet storing unit to detect the presence or absence of the
sheets, characterized in that the contact consists of a first
contact extending downwardly from a higher position than the sheet
storing unit and a second contact extending upwardly from a lower
position than the sheet storing unit.
According to the sheet feeding apparatus as the first aspect of the
present invention, the separated contact into two parts provided at
both upper and lower sides of the sheet storing unit detect whether
sheets are present or not in the sheet storing unit and their
detection results to be used for determining a variety of judgments
and carrying out various control based on the judgment results.
A sheet feeding apparatus as a second aspect of the present
invention is a sheet feeding apparatus according to the first
aspect, characterized in that the sheet detector includes a first
sheet detector arranged at a position higher than the sheet storing
unit and a second sheet detector arranged at a position lower than
the sheet storing unit, and the first contact is provided in the
first sheet detector while the second contact is provided in the
second sheet detector.
According to the sheet feeding apparatus as the second aspect of
the present invention, the contacts of the two sheet detectors
provided at both upper and lower sides of the sheet storing unit
detect whether sheets are present or not in the sheet storing unit,
respectively and the combination of their detection results is used
for determining a variety of judgments and carrying out various
control based on the judgment results.
A sheet feeding apparatus as a third aspect of the present
invention is a sheet feeding apparatus according to the second
aspect, characterized in that the first and second contacts are
configured so that a first detecting area of the first contact for
detecting the sheets stored in the sheet storing unit, and a second
detecting area of the second contact for detecting the sheets
stored in the sheet storing unit partially overlap each other.
According to the sheet feeding apparatus as the third aspect of the
present invention, the two areas detected by respective contacts
partially overlap each other, whereby the sheets stored in the
sheet storing unit can be detected by at least one of the
contacts.
A sheet feeding apparatus as a fourth aspect of the present
invention is a sheet feeding apparatus according to the third
aspect, characterized by further comprising: a height detector for
detecting the height of the uppermost one of the sheets stored in
the sheet storing unit; an elevation/lowering mechanism for
elevating or lowering the sheet storing unit at a predetermined
speed within a predetermined range; and a control circuit for
controlling the elevation/lowering mechanism in response to a
detection result of the height detector so as to keep the height of
the sheet storing unit where the height of the uppermost one of the
sheets stored in the sheet storing unit is equal to a height for
picking up the sheets within the first and second detecting
areas.
According to the sheet feeding apparatus as the fourth aspect of
the present invention, when the sheet storing unit stores a large
number of the sheets, a height of the uppermost sheet of the sheets
stored in the sheet storing unit is kept at a predetermined height
where a sheet is picked up by the sheet feeding mechanism.
A sheet feeding apparatus as a fifth aspect of the present
invention is a sheet feeding apparatus according to the fourth
aspect, characterized by further comprising: a sheet volume
calculating circuit for determining a volume of the sheets stored
in the sheet storing unit based on a detection result of the first
contact and a detection result of the second contact.
According to the sheet feeding apparatus as the fifth aspect of the
present invention, the volume of the sheets stored in the sheet
storing unit is roughly determined by combining the detection
results of the two contacts.
A sheet feeding apparatus as a sixth aspect of the present
invention is a sheet feeding apparatus according to the fifth
aspect, characterized by further comprising: a sheet storing unit
position detector for detecting whether or not the sheet storing
unit is at its lower-limit position within the predetermined range;
and a control circuit for controlling the elevation/lowering
mechanism to elevate the sheet storing unit at a speed higher than
the predetermined speed when the sheet storing unit position
detector detects that the sheet storing unit is at the lower-limit
position and the sheet volume calculating circuit determines that
the volume of the sheets stored in the sheet storing unit is the
volume which is not detected within the first detecting area.
According to the sheet feeding apparatus as the sixth aspect of the
present invention, the sheet storing unit is elevated at a speed
higher than the normal speed from its lower-limit position when it
is determined that a small number of sheets are stored in the sheet
storing unit positioned at the lower-limit position where a maximum
of the sheets can be stored.
An image reading apparatus according to the present invention is
characterized by the sheet feeding apparatus according to any of
the above described aspects.
An image forming apparatus according to the present invention is
characterized by the sheet feeding apparatus according to any of
the above described aspects.
Further, the image forming apparatus according to the present
invention is characterized by the image reading apparatus equipped
with the sheet feeding apparatus according to any of the above
described aspects.
Also, an image forming apparatus according to the present invention
is an image forming apparatus characterized by comprising: an image
reading apparatus in which a sheet feeding apparatus is
incorporated, the sheet feeding apparatus comprising: a sheet
storing unit in which a number of sheets are stored in a stack; a
sheet feeding mechanism for picking up and feeding out the sheets
stored in the sheet storing unit in a sequence from the uppermost
one; and a sheet detector having a contact for contacting the
sheets stored in the sheet storing unit to detect the presence or
absence of the sheets; wherein the contact consists of a first
contact extending downwardly from a higher position than the sheet
storing unit and a second contact extending upwardly from a lower
position than the sheet storing unit; the sheet detector includes a
first sheet detector arranged at a position higher than the sheet
storing unit and a second sheet detector arranged at a position
lower than the sheet storing unit, and the first contact is
provided in the first sheet detector while the second contact is
provided in the second sheet detector; and the first and second
contacts are configured so that a first detecting area of the first
contact for detecting the sheets stored in the sheet storing unit
and a second detecting area of the second contact for detecting the
sheets stored in the sheet storing unit partially overlap each
other; a height detector for detecting the height of the uppermost
one of the sheets stored in the sheet storing unit; an
elevation/lowering mechanism for elevating or lowering the sheet
storing unit at a predetermined speed within a predetermined range;
a control circuit for controlling the elevation/lowering mechanism
in response to a detection result of the height detector so as to
keep the height of the sheet storing unit where the height of the
uppermost one of the sheets stored in the sheet storing unit is
equal to a height for picking up the sheets within the first and
second detecting areas; a sheet volume calculating circuit for
determining a volume of the sheets stored in the sheet storing unit
based on a detection result of the first contact and a detection
result of the second contact; a memory unit for storing the data of
images read by the image reading apparatus and inputted from the
external; an image forming unit for forming images based on the
data stored in the memory unit; and a control circuit for setting
an allocated capacity of the memory unit for storing the data of
images read by the image reading apparatus in response to the
volume of the sheets stored in the sheet storing unit calculated by
the sheet volume calculating circuit, and for permitting the input
of images from the external when the allocated capacity of the
memory unit for storing the data of images read by the image
reading apparatus is not larger than a predetermined value.
According to such image forming apparatus, the memory unit stores
at a small storage area for storing the data of images when the
number of the sheets stored in the sheet storing unit is small
while the remaining storage area can be allocated for other
processing.
The above and further objects and features of the present invention
will more fully be apparent from the following detailed description
with accompanying drawings.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an explanatory view of a prior art;
FIG. 2 is an explanatory view of another prior art;
FIG. 3 is a longitudinally cross sectional view illustrating an
example of the overall schematic configuration of an image reading
apparatus equipped with an ADF (automatic document feeder) in which
a sheet feeding apparatus according to the present invention is
built in;
FIG. 4 is a schematic view illustrating an arrangement state and
detecting areas of a lower document detector, an upper document
detector, and a document tray lower-limit position detector which
can detect a document tray being positioned at the lower-limit
(reference) position;
FIG. 5 is a schematic view illustrating an operation state of the
lower document detector, the upper document detector, and the
document tray lower-limit position detector for detecting the
document tray being positioned at the lower-limit (reference)
position;
FIG. 6 is a schematic view illustrating an operation state of the
lower document detector, the upper document detector, and the
document tray lower-limit position detector for detecting the
document tray being positioned at the lower-limit (reference)
position;
FIG. 7 is a schematic view illustrating an operation state of the
lower document detector, the upper document detector, and the
document tray lower-limit position detector for detecting the
document tray being positioned at the lower-limit (reference)
position;
FIG. 8 is a view illustrating an example of the relationship
between an actuator of the lower document detector, an actuator of
the upper document detector, the distance between the two
actuators, and the thickness (height) of a stack of the documents
set on the document tray;
FIG. 9 is a block diagram illustrating functional configuration of
an image reading apparatus according to one embodiment of the
present invention whose mechanical configuration is shown in FIG.
3;
FIG. 10 is a schematic view illustrating a configuration example of
an operation unit of the image reading apparatus of the present
invention;
FIG. 11 is a longitudinal cross sectional view of a digital
multiple function printer as an image forming apparatus for forming
an image by reading an image of a document by the image reading
apparatus of the present invention;
FIG. 12 is a flowchart showing a procedure of operation of a
digital multiple function printer in which a sheet feeding
apparatus of the present invention is built in;
FIG. 13 is a flowchart showing a procedure of operation of a
digital multiple function printer in which a sheet feeding
apparatus of the present invention is built in;
FIG. 14 is a flowchart showing a procedure of operation of a
digital multiple function printer in which a sheet feeding
apparatus of the present invention is built in;
FIG. 15 is a flowchart showing a procedure of operation of a
digital multiple function printer in which a sheet feeding
apparatus of the present invention is built in; and
FIG. 16A and FIG. 16B are graphic diagrams showing control states
(control states of the rotational speed of the motor) of an
elevation/lowering motor in the flowcharts of FIG. 14 and FIG.
15.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
The best modes for embodying the present invention will be
described in more detail referring to the accompanying drawings.
The description starts with a configuration example of a sheet
feeding apparatus according to the present invention in conjunction
with the longitudinal cross sectional view of FIG. 3 showing the
mechanical configuration of an image reading apparatus equipped
with an ADF (automatic document feeder) in which the sheet feeding
apparatus of the present invention is built in.
The image reading apparatus 1 is composed roughly of an optical
system 2 and an ADF (Automatic Document Feeder) 3 disposed above
the optical system 2, and functions as a scanner unit of a copy
apparatus, facsimile apparatus or the like. Note that the image
reading apparatus 1 exemplified in FIG. 3 is capable of reading
images formed on both surfaces of a document described in detail
later.
The optical system 2 comprises a CCD reading unit (CCD: Charge
Coupled Device) 11 serving as a first reading unit disposed under a
document table 12 which is a plane glass plate (platen glass). The
CCD reading unit 11 is fixed at a predetermined position, and is
composed of an imaging lens 11a, a CCD image sensor 11b disposed at
a position where an image is focused by the imaging lens 11a, and
the like. As a result, disposed positions of respective components
are determined so that an image of a document supported in plane
condition and set on the document table 12 as a plane glass plate
is focused at the CCD image sensor 11b of the CCD reading unit 11
by a light source unit 13 and a mirror unit 14.
The light source unit 13 comprises a light source 13a; a condense
mirror 13b for condensing illumination light, irradiated from the
light source 13a for reading, onto a predetermined reading position
on the document table 12 from the under side of the document table
12; a slit 13c for passing only the reflected light from the
document; and a reflecting mirror 13d for changing the optical path
of the light passed through the slit 13c by 90.degree..
The mirror unit 14 comprises a pair of reflecting mirrors 14a and
14b with reflecting surfaces arranged orthogonally each other for
further changing, by 180.degree., the optical path from the
reflecting mirror 13d of the light source unit 13 so as to become
the reverse direction and parallel to the document table 12 at
further lower position.
As denoted by reference numerals 13e and 13f, by moving the light
source unit 13 in the direction of an arrow 15 in the figure (a
sub-scanning direction) parallel to the surface of the document
table 12, and similarly by moving the mirror unit 14 in the
direction of the arrow 15 (a sub-scanning direction) parallel to
the surface of the document table 12, it is configured that the
image of a document set on the document table 12 can be read. At
this time, it is necessary to adjust the moving speed of the mirror
unit 14 to be V/2 when the moving speed of the light source unit 13
is V. These light source unit 13 and mirror unit 14 are moved by a
stepping motor 42 not shown (see FIG. 9).
Note that the CCD reading unit 11 may be designed to focus
reflected light generated by reflecting the light irradiated from
the light source 13a by the document onto the CCD image sensor 11b
through the imaging leans 11a while a unit of reduced reading
optical system or equal-magnification reading optical system
constructed by at least the imaging lens 11a, the CCD image sensor
11b and the light source 13a as one unit scan at moving speed
V.
Moreover, this optical system 2 comprises another document table 16
in a position separated by an appropriate distance from the one end
portion, specifically one end portion on the left side in FIG. 3,
of the document table 12 in the sub-scanning direction. The light
source unit 13 can read the image on one surface (hereinafter this
surface which is the lower surface on the document table 16 in FIG.
3 is referred to as the front surface) of the document conveyed on
the document table 16, in a state in which the light source unit 13
is stationary just under the document table 16 (position shown by
reference numeral "Pos1" in FIG. 3). A sheet discharge tray 17 for
receiving and stacking documents whose surfaces are read during
conveying on the document table 16 is provided near the exit of
such documents.
On the other hand, the ADF 3 comprises a CIS (Contact Image Sensor)
21 serving as a second reading unit at a position shown by "Pos2"
in FIG. 3 on the upper side of the document table 16. The CIS 21
comprises an image sensor at the under surface thereof for reading
image. The ADF 3 picks up one sheet of the documents set in a
stacked state on the document tray 22, and causes the CIS 21 to
read the image on the other surface (hereinafter this surface which
is upper surface on the document table 16 in FIG. 3 is referred to
as the rear surface) of the document.
For realizing such functions, the ADF 3 further comprises various
rollers R1 through R10, detectors S0 through S8, a curved
conveyance path 23, a resist/skew correction area 24, and the like.
Note that the CIS 21 is configured as a contact type image sensor
comprising, for example, an array image sensor, an array light
guiding means (a lens array such as a SELFOC lens), a light source
(an LED array light source or a fluorescent lamp), and the
like.
Note that the various rollers R1 through R10 are driven by a
document conveyance motor 43 not shown in FIG. 3 (see FIG. 9).
Further, although it is described in detail later, a guide-in
roller clutch 44 (see FIG. 9) is connected to the guide-in roller
R1 and the separate roller R2 that are connected with transmitting
mechanism such as a belt, and a resist roller clutch 45 (see FIG.
9) is connected to either of a pair of resist rollers R8 and R9. By
connecting or disconnecting these clutches 44, 45 under the control
of a later-described control unit 41 (see FIG. 9), the driving
force of the document conveyance motor 43 is transmitted to the
guide-in roller R1, separate roller R2 and the pair of resist
rollers R8 and R9, or cut off.
The document tray 22 is an electric tray (elevation/lowering tray
elevating and lowering by an electric motor). The image reading
unit 1 enters standby state for waiting an instruction for reading
documents when setting of the documents on the document tray 22 is
detected by combination of detecting results of a contact type
lower document detector S1 composed of an actuator S1a as a contact
which rotates by contacting with a leading end of a document having
been set on the document tray 22 and a sensor body S1b for
detecting the rotation of the actuator S1a, and a contact type
upper document detector S1' composed of an actuator S1a' as a
contact and a sensor body S1b' similar to the actuator S1a and the
sensor body S1b.
Then, the elevation of the document tray 22 starts at a
predetermined timing by the control procedure which will be
described later in more detail. When elevation of the document tray
22 starts, it reaches a position where the uppermost one of the
stack of the documents stored on the document tray 22 presses up
the guide-in roller R1 which is supported by an arm 25 capable of
elevating and lowering. Simultaneously, the pressing up of the
guide-in roller R1 is detected by the guide-in roller position
detector S2R1. Then, the elevation of the document tray 22 is
stopped and may be kept at the height of the position in the
standby state.
FIG. 4 is a schematic view illustrating an arrangement with their
detecting areas of the lower document detector S1, the upper
document detector S1', and the document tray lower-limit position
detector S8 for detecting that the document tray 22 is positioned
at the lower limit position (reference position). FIG. 5 to FIG. 7
are schematic views explaining their operation state.
As shown in FIG. 4, provided beneath the arm 25 is a document
leading end regulating plate 28 for correctly setting the documents
so as to be a state where the leading ends of the documents on the
document tray 22 are uniformly aligned and at a position where the
upper side of the uppermost one of the stack of the documents on
the documents tray 22 contacts with the under side of the guide-in
roller R1 when the document tray 22 elevates. The document leading
end regulating plate 28 is formed as a flat plate extending in
parallel with the axial direction of the guide-in roller R1 and a
lower end thereof bent towards the document tray 22 as a projection
which configures as a stopper 280 at the lower-limit position of
the document tray 22.
Accordingly, when the document tray 22 lowers, its bottom becomes
into contact with the upper side of the stopper 280 to inhibit
further downward movement as denoted by the broken line in FIG. 4.
In this state, the actuator S8a of the document tray lower-limit
position detector S8 rotates at a predetermined angle by contacting
with the bottom of the document tray 22. By detecting the rotation
of the actuator S8a by the sensor body S8b, the document tray
lower-limit position detector S8 detects that the document tray 22
is at its lower-limit position.
The lower document detector S1 is fixed at a position slightly
lower than the bottom surface of the document tray 22 so that its
sensor body S1b does not disturb the document tray 22 at its
lower-limit position. Also, the actuator S1a as the contact of the
lower document detector S1 is a bar-like contact which is directed
upwardly and capable of rotating about one end portion as the
rotational center at the side of the sensor body S1b towards the
feeding direction of the documents. The actuator S1a of the lower
document detector S1 has such a length that its tip end projects
slightly upward from the center of the elevation/lowering range of
the document tray 22 during its rotation. In other wards, the
detection range of the actuator S1a of the lower document detector
S1 covers to the whole lower range between the lower-limit position
and the center position of the elevation/lowering range of the
document tray 22 and a portion slightly entering the upper side
from this lower range (in the upper half range which will be
described later).
Also, the document tray 22 and the document leading end regulating
plate 28 have notches provided therein for avoiding the rotation
range of the actuator S1a, thus permitting no collision of the
actuator S1a of the lower document detector S1 against the document
tray 22 or the document leading end regulating plate 28.
Meanwhile, the upper document detector S1' is also fixed at a
position slightly upper than the upper surface of the document tray
22 so that its sensor body S1b' does not interrupts the document
tray 22 positioned at the upper-limit position (more precisely,
where the document tray 22 contacts with the guide-in roller R1
when documents are not set on the document tray 22). The actuator
S1a' as the contact of the upper document detector S1' is a
bar-like contact which is directed downwardly and capable of
rotating about one end portion as the rotational center at the side
of the sensor body S1b' towards the feeding direction of the
documents. The actuator S1a' of the upper document detector S1' has
such a length that its tip end projects slightly downward from the
center position of the elevation/lowering range of the document
tray 22 during the rotation. In other wards, the detection range of
the actuator S1a' of the upper document detector S1' covers to the
whole upper range between the upper-limit position and the center
position of the elevation/lowering range of the document tray 22
and a portion slightly entering the lower side from this upper
range.
Also, the document tray 22 and the document leading end regulating
plate 28 have notches provided therein for avoiding the rotation
range of the actuator S1a', thus permitting no collision of the
actuator S1a' of the upper document detector S1' against the
document tray 22 or the document leading end regulating plate
28.
FIG. 5 is a schematic view of a state where a stack of the
documents whose quantity makes its uppermost not reach the actuator
S1a' of the upper document detector S1' when the document tray 22
is at the lower-limit position. In this state, the document tray
lower-limit position detector S8 detects that the document tray 22
positions at the lower-limit position. Also, as the actuator S1a of
the lower document detector S1 rotates because it contacts with the
leading end of the stack SB of the documents set on the document
tray 22, the lower document detector S1 is turned to the detection
(ON) state with its sensor body S1b detecting the rotation of the
actuator S1a. On the other hand, as the actuator S1a' of the upper
document detector S1' does not rotate because it does not contact
with the stack SB of the documents set on the document tray 22, the
upper document detector S1' is turned to the non-detection (OFF)
state with its sensor body S1b' detecting no rotation of the
actuator S1a'.
FIG. 6 is a schematic view of a state where documents whose
quantity makes the uppermost layer of the stack SB of the documents
reach the actuator S1a' of the upper document detector S1' when the
document tray 22 is at the lower-limit position. In this state, the
document tray lower-limit position detector S8 detects that the
document tray 22 positions at the lower-limit position. Also, as
the actuator S1a of the lower document detector S1 rotates because
it contacts with the leading end of the stack SB of the documents
set on the document tray 22, the lower document detector S1 is
turned to the detection (ON) state with its sensor body S1b
detecting the rotation of the actuator S1a. Further, as the
actuator S1a' of the upper document detector S1' rotates because it
contacts with the leading end of the stack SB of the documents set
on the document tray 22, the upper document detector S1' is turned
to the detection (ON) state with its sensor body S1b' detecting
rotation of the actuator S1a'.
FIG. 7 is a schematic view of a state where the document tray 22
gradually elevates and further elevates so that the lowermost one
of the stack SB of the documents set on the document tray 22 comes
out of the detecting area of the actuator S1a of the lower document
detector S1 when the stack SB of the documents having a small
number of documents are set on the document tray 22, or a state
where the stack SB of the documents having a small number of
documents is set on the document tray 22 and the document tray 22
is standby state at its illustrated position. In this state, the
document tray lower-limit position detector S8 detects that the
document tray 22 dos not positions at the lower-limit position.
Also, as the actuator S1a of the lower document detector S1 does
not rotate because it does not contact with the leading end of the
stack SB of the documents set on the document tray 22, the lower
document detector S1 is turned to the non-detection (OFF) state
with its sensor body S1b detecting the no rotation of the actuator
S1a. On the other hand, as the actuator S1a' of the upper document
detector S1' rotates because it contacts with the leading end of
the stack SB of the documents set on the document tray 22, the
upper document detector S1' is turned to the detection (ON) state
with its sensor body S1b' detecting rotation of the actuator
S1a'.
FIG. 8 is a view showing an example of the relationship between the
rotation of the actuator S1a of the lower document detector S1 and
the actuator Sla' of the upper document detector S1', and the
distance between the two centers of the rotation of both the
actuators S1a and S1a' and the thickness (height) of the stack of
the documents set on the document tray 22.
In the example, the effective length (from the rotational center to
the tip end) L1 of the actuator S1a of the lower document detector
S1 is set to 33 mm while the effective length L2 of the actuator
S1a' of the upper document detector S1' is set to 24 mm. Also, the
free height (from the rotational center as the base to the tip end
when not in contact with the documents) H1 of the actuator S1a of
the lower document detector S1 is set to 27 mm while the free
height H2 of the actuator S1a' of the upper document detector S1'
is set to 22 mm. The height H3 extending from the rotational center
as the base of the actuator S1a of the lower document detector S1
to the rotational center of the actuator S1a' of the upper document
detector S1' is set to 42 mm.
By setting above data, the height (thickness) h1 of the stack of
the documents set on the document tray 22 which is hardly detected
with the upper document detector S1' is 10 mm equivalent to 100
sheets of the document. The height (thickness) of the stack of the
documents set on the document tray 22 which can be detected with
the lower document detector S1 is a sum of h1 and h2 (e.g. 7 mm
equivalent to 70 sheets of the document) which is then 17 mm.
Assuming that the maximum number of documents to be set on the
document tray 22 is 200, the height h3 of the maximum documents set
on the document tray 22 is 20 mm. In addition, the relationship
between the number of documents and the height (thickness) of it is
an approximate based on new and unused PPC paper and is not
exactly.
It is noted that the actuator S1a of the lower document detector S1
is longer in the effective length than the actuator S1a' of the
upper document detector S1' because the rotational center of the
actuator S1a of the lower document detector S1 has to position
lower than the bottom of the document tray 22. The longer the
length of one of the two actuators, the shorter the length of the
other actuator may be determined. It is however preferred in
practice that the actuator S1a' of the upper document detector S1'
other than the actuator S1a of the lower document detector S1 is
set to a shorter length as it always comes into contact with the
documents during the feeding operation.
In case that the document tray 22 set with the document elevates
and stays at its standby position for a predetermined period of
time after no start signal for the reading operation is entered,
its standby state may be held. It is however preferred for
preventing any deformation of the guide-in roller R1 to lower the
document tray 22 to an appropriate height or the lower-limit
position before holding at the standby state.
Then, upon giving a feeding start signal of the document, when the
document tray 22 is positioned at a relatively lower position in
the standby state, the document tray 22 elevates until the guide-in
roller position detector S2 detects that the guide-in roller R1 is
pressed up. At this time, the guide-in roller R1 is driven and
rotated. As a result, the uppermost one of the stack of the
documents set on the document tray 22 will be fed out in a
sequence.
The pair of separate rollers R2 and R2a are provided at the
downstream side of the guide-in roller R1 along the document
feeding direction. Meanwhile, the guide-in roller R1 is supported
at the tip end of the arm 25, and the portion of the base side of
the arm 25 is rotatably supported by the rotational axis of the
separate roller R2. As the guide-in roller R1 is downwardly forced
by its own weight or any other force, it comes into contact with
the uppermost one of the stack of the documents set on the document
tray 22. Also, the lower limit position when the guide-in roller R1
lowers is regulated by a stopper (not shown) so as to prevent
unnecessary lowering.
The arm 25 has a projection provided on one side thereof which can
be detected by the guide-in roller position detector S2 composed of
an optical sensor or the like for detecting the height of the
guide-in roller R1 based on the angle of rotation of the arm 25.
Although the guide-in roller position detector S2 is arranged to
directly detect the projection on the arm 25 for detecting the
position of the guide-in roller R1 in this embodiment, it may be
positioned apart from the arm 25. In the latter case, the height of
the arm 25 may be detected with a help of a movable joining
mechanism or the like.
The separate roller R2 comprises a roller R2a having a torque
limiter (a friction pad, for example, may be used instead) which
faces and presses the separate roller R2. Thus the documents are
surely separated and conveyed one by one without feeding the
documents in an overlapped state. Therefore, even when plural
sheets of document are picked up by the guide-in roller R1, only
the topmost layer of documents adhering to the guide-in roller R1
is picked up by the pair of separate rollers R2 and R2a, and is
conveyed to the curved conveyance path 23.
Note that whether or not a document was certainly separated and
supplied by the pair of separate rollers R2 and R2a is detected by
the fed sheet detector S3 composed of an actuator S3a which rotates
by contacting with a document and a sensor body S3b for detecting
the rotation of the actuator S3a based on the time period during
which the actuator S3a is contacting with a document. Then, the
document certainly separated by the pair of separate rollers R2 and
R2a is conveyed at a predetermined timing to the curved conveyance
path 23 on the downstream side.
In the curved conveyance path 23, the document is conveyed by the
conveyance rollers R3 through R7. At this time, whether the
document is conveyed in the curved conveyance path 23 forcibly or
not is detected by the fed sheet detector S4 composed of an
actuator S4a which rotates by contacting with a leading end of a
document and a sensor body S4b which detects the rotation of the
actuator S4a and detects the discharge of the document from the
curved conveyance path 23. The curved conveyance path 23 has a
curvature capable of conveying any kind of document in a stable
manner. Concretely, the curved conveyance path 23 is constructed
with a curvature capable of smoothly conveying the thickest
document, i.e., the sturdiest document, among readable documents by
the image reading apparatus 1.
The document discharged from the curved conveyance path 23 is
conveyed to the resist/skew correction area 24. When the leading
end of the document is detected by the fed sheet detector S5
positioned in front of the pair of resist rollers R8 and R9 near
the exit of the resist/skew correction area 24, rotation of the
pair of resist rollers R8 and R9 is once stopped. In this state,
the leading end of the document is caused to collide with the joint
of the pair of resist rollers R8 and R9 by a conveyance force from
the upstream side over a predetermined time, and a resist and skew
correction is performed. The fed sheet detector S5 is composed of
an actuator S5a which rotates by contacting with the leading end of
the document and a sensor body S5b which detects the rotation of
the actuator S5a.
The resist/skew correction area 24 extends from the position of the
pair of resist rollers R8 and R9 at the most down stream side of
the curved conveyance path 23 to the pair of resist rollers R8 and
R9. The resist/skew correction area 24 is designed so that a
document S is in a substantially straightened condition between the
pair of conveyance rollers R6 and R7 and the pair of resist rollers
R8 and R9 and is free as much as possible from the guide surface of
the conveyance path so as to allow the above-mentioned resist/skew
correction of document to be performed in the resist/skew
correction area 24 ranging from the pair of conveyance rollers R6
and R7 positioned on the downstream side of the curved conveyance
path 23 to the pair of resist rollers R8 and R9. Note that the
distance between the pair of conveyance rollers R6 and R7 and the
pair of resist rollers R8 and R9 may be set by ensuring at least
the length of the smallest document, in the conveying direction,
among documents that can be handled by the ADF (document feeder).
In other words, the shorter the trailing end portion of the
document remaining in the curved conveyance path 23, the smoother
the resist/skew correction of document is performed.
The conveyance of the document, for which the resist/skew
correction was made in the resist/skew correction area 24 described
above, is resumed at a predetermined timing, and the document is
conveyed to the first reading position Pos1 for exposing and
scanning the front surface of the document. Further, the document
passes through a second reading position Pos2 for exposing and
scanning the rear surface of the document. The light source unit 13
faces the first reading position Pos1, and the CIS 21 faces the
second reading position Pos2.
The document whose image on the front surface or images on both the
front and rear surfaces were thus read is discharged onto the sheet
discharge tray 17, which is supported on a side surface of the
image reading apparatus 1 located in a lower position than the
document discharge point, by the pair of discharge rollers R10 and
R11 (the discharge roller R10 is provided on the ADF 3 side and the
discharge roller R11 is provided on the optical system 2 side). The
confirmation of this document discharge operation is detected by
the discharged sheet detector S6 composed of an actuator S6a which
enters rotation state during the document is passing and a sensor
body S6b which detects the rotation state of the actuator S6a.
The above-described operations are repeated one after another until
all the documents set on the document tray 22 are fed, and all the
documents which have been read are discharged one by one onto the
sheet discharge tray 17.
By the way, since the height of the stack of the documents is
lowered when the documents are fed one by one, the document tray 22
is controlled to be elevated by an amount corresponding to the
lowering of the position of the stack of the documents so as to
always keep a predetermined height relationship between the topmost
layer of the stack of the documents and the guide-in roller R1.
Therefore, the document tray 22 can swing centered by a fulcrum 22a
provided on the opposite end portion to the guide-in roller R1, and
a rib 22b provided on the opposite end portion to the fulcrum 22a
can be elevated by pushing it up by an elevation/lowering plate 31.
An end of the elevation/lowering plate 31 opposite to the rib 22b
is fixed to a plate supporting shaft 32. To the plate supporting
shaft 32, an elevation/lowering mechanism unit 34 composed of a
transmission member (gear) train and driven and rotated by an
elevation/lowering motor 33 is connected. Accordingly, the plate
supporting shaft 32 is driven and rotated by the elevation/lowering
motor 33 through the elevation/lowering mechanism unit 34, the
elevation/lowering plate 31 rotates to push up the rib 22b
resulting the document tray 22 is elevated, on the other hand, the
document tray 22 being lowered by its own weight.
The position (home position denoted by reference numeral HP in FIG.
3) of this document tray 22 during standby state is determined by
rotational position of the elevation/lowering plate 31, and driving
and controlling the elevation/lowering motor 33 of the
elevation/lowering mechanism unit 34 by the later-described control
unit, and kept by driving and controlling the elevation/lowering
mechanism unit 34 by the later-described control unit on the basis
of a detection signal of the guide-in roller position detector S2.
The position of the document tray 22 during standby state can be
set arbitrarily by a later-described operation unit 46 according to
a frequently set number of documents on the document tray 22 in an
ordinary general use condition, and can be set suitably by a
service person or a user.
Further, the document tray 22 can be elevated/lowered and displaced
within a range between the height position of the entrance side and
the height position of the exit side of the curved conveyance path
23, which are inevitably formed by the curved conveyance path 23
that was set to guarantee stable conveyance of documents as
described above. When the document tray 22 is moved in the lowering
direction within this range, the interval between the document tray
22 and the guide-in roller R1 increases, and therefore a large
amount of documents can be set and fed one by one by elevating the
topmost layer of the large amount of documents set on the document
tray 22 to a state capable of being fed to the entrance of the
curved conveyance path 23.
Moreover, the document tray 22 has the document regulating plate 30
for regulating the set position of documents by aligning the sides
of the documents with user's hand. The position of this document
regulating plate 30 is detected by the first document size detector
S0 for detecting the width of the document. Note that the document
tray 22 is also provided with the second document size detector S7
(see FIG. 9) for detecting the length of the document (the length
in the document feed direction). The size of a document set on the
document tray 22 is detected by these first and second document
size detectors S0 and S7, and a sheet for image forming is selected
on the basis of the detection results, and the detection results
are also used by the later-described control unit for the control
of the height position of the document tray 22.
In the meantime, when reading a document on the document table 12,
the light source unit 13 is moved from a position Pos3 (the start
position of the light source unit 13 when reading a stationary
position) toward a position Pos4 (the return position of the light
source unit 13 when reading the largest document) in FIG. 3 by only
a predetermined distance according to a document size detected by a
third document size detector (not shown in FIG. 3, see FIG. 9) for
detecting the size of a document set on the document table 12.
On the other hand, when reading the document with conveying, the
light source unit 13 is stopped at the reading position Pos1 (the
position of the light source unit 13 when reading a moving
document). Moreover, the light source unit 13 uses either a
position between the position Pos3 and the position Pos4, or a
position between the position Pos3 and the reading position Pos1,
as a home position based on the detection result of a light source
unit detector serving as the position detector of the light source
unit 13. Therefore, when the light source unit 13 is not in use,
i.e., is on standby, it is stopped in this home position.
Here, in order to read the document set on the document table 12, a
portion of the ADF 3 located on the back side of the image reading
apparatus 1 (the back side in FIG. 3) is movably supported by a
hinge (not shown) attached between the ADF 3 and the optical system
2. The ADF 3 moves around this hinge as a movement support and
opens upward with respect to the document tray 12. In other words,
by opening the ADF 3 by moving it upward, the top surface of the
document table 12 of the image reading apparatus 1 can be opened
from the front side in FIG. 3, and consequently documents of types
that can not be conveyed by the ADF 3 because they are not in a
sheet form, for example, a book material and a bound document, can
be set on the document table 12. Note that a document mat 35 formed
of an elastic material is provided on the bottom surface of the ADF
3, i.e., the surface facing the document table 12.
The image reading apparatus 1 thus constructed can read documents
in three modes, namely, a stationary read mode, a moving read mode,
and a double-side read mode. The stationary read mode is a mode in
which the light source unit 13 and the mirror unit 14 are scanned
(moved) in the direction shown by the arrow 15 and the image of a
document such as a book material set on the document table 12 is
read by the CCD reading unit 11. The moving read mode and the
double-side read mode are modes in which the images of documents
set on the document tray 22 are read by automatically feeding one
sheet at a time by the ADF 3. In the moving read mode, the
documents are read by the CCD reading unit 11 or the CIS 21,
whereas, in the double-side read mode, the images of documents are
read using both of the CCD reading unit 11 and the CIS 21.
Note that in this embodiment, the maximum number of documents that
can be set on the document tray 22 is around 200 sheets if the
documents have a thickness of, for example, an ordinary copy sheet
or so.
FIG. 9 is a block diagram showing a functional configuration of the
image reading apparatus 1 according to this embodiment whose
mechanical configuration is shown in FIG. 3. In FIG. 9, the
components same as or corresponding to those shown in FIG. 3 are
designated with the same reference numeral, and the explanation
thereof is omitted.
To the control unit 41 composed of a microcomputer, etc., the
detection results of the first and second document size detectors
S0 and S7 for detecting the size of the document set on the
document tray 22 and the detection result of the third document
size detector S9 disposed on the optical system 2 side for
detecting the size of the document set on the document table 12 are
supplied. The control unit 41 switches control of the sheet to be
used and timing, on the basis of the detection results of these
document size detectors S0, S7 and S9.
At the reading of the document using the CCD reading unit 11, the
control unit 41 drives and controls the stepping motor 42 to move
the light source unit 13 and the mirror unit 14 as described above,
and controls the light source 13a and the CCD image sensor 11b
according to the position of the light source unit 13 detected by
the light source unit detector S10 so as to read the image of the
document.
On the other hand, in the reading of the document using the ADF 3,
the control unit 41 drives and controls the elevation/lowering
motor 33 on the basis of the detection result of the guide-in
roller position detector S2; keeps the topmost surface of a stack
of the documents set on the document tray 22 at a fixed height;
conveys the documents by controlling the document conveyance motor
43, the guide-in roller clutch 44 and the resist roller clutch 45
based on the detection results of each detector S3 through S6 until
the lower document detector S1 and the upper document detector S1'
detect that all the documents on the document tray 22 have been
fed; and reads the images of the documents by controlling the CCD
image sensor 11b and/or the CIS 21.
Moreover, the control unit 41 displays necessary information on the
operation unit 46 (see FIG. 10) composed of a liquid crystal touch
panel, etc., and receives an input operation applied to the
operation unit 46.
Further, reference numeral 40 denotes an image memory which is used
for storing image data read described above. Processing procedure
for using the image memory 40 is described later.
FIG. 10 is a schematic view showing an example of the structure of
the operation unit 46 of the image reading apparatus 1 according to
the present invention. Although not shown in FIG. 3, the operation
unit 46 is positioned on the top surface of the image reading
apparatus 1, and comprises various keys K1 through K8 and an
operation panel P composed of a liquid crystal touch panel or the
like.
The various keys K1 through K8 provided in the operation unit 46
include K1 as a ten-key keypad for inputting numerals, K2 as an
Interrupt key for interruption processing, K3 as a Clear key, K4 as
an All Clear (all delete) key, K5 as a Start key for starting to
read a document, and K6, K7 and K8 as function switching keys for
selecting a facsimile function, a printer function and a copy
function, respectively. Note that when the image reading apparatus
1 of the invention is built in a digital multiple function printer
(MFP) 100, the digital multiple function printer 100 functions as a
copy apparatus by operation of the copy key K8. In this case, the
Start key K5 functions as a key for instructing to start copy.
On the operation panel P various screens are displayed and changed.
In theses screens, touch keys for setting various conditions, and
various condition setting is possible when user directly pushes
those touch keys. Further, the operation panel P is constructed so
as to display various guidance and warnings for operation.
FIG. 11 is a vertical cross sectional view showing the schematic
configuration of the digital multiple function printer 100 as an
image forming apparatus for reading image of the document and
forming image by above-mentioned image reading apparatus. In such
the image forming apparatus, above-mentioned sheet feeding
apparatus of the present invention is built in not only the image
reading unit for reading image from sheet-like document but also a
construction for supplying recording sheet (sheet-like copy paper)
to an image forming apparatus.
In the digital multiple function printer 100, the image reading
apparatus 1 shown in FIG. 3 mentioned above is built in as the
reading unit 110. Document image read by the reading unit 110 is
transferred as an image data to an image data inputting unit (not
shown), and predetermined image processing is performed on the
image data, then the image data is stored temporarily in the image
memory 40 shown in FIG. 9. Thereafter, when an output instruction
is given, the image data stored in the image memory 40 is read and
transmitted to a laser writing unit 227 that is an optical writing
apparatus of an image forming unit 210.
The laser writing unit 227 comprises a semiconductor laser light
source for emitting laser light according to the image data
transferred from the image memory 40 or external device; a polygon
mirror for deflecting the laser light at equal angular velocity;
and a f-0 lens for correcting the laser light deflected at equal
angular velocity so that the laser light is deflected at equal
angular velocity on a photoconductor drum 222. Note that although
this embodiment uses the laser writing unit 227 as the optical
writing apparatus, it may be possible to employ a fixed scanning
type optical writing head unit using a light emitting element
array, such as LED (Light Emitting Diode) and EL (Electro
Luminescence).
Disposed around the photoconductor drum 222 are an electrizer 223
for charging the photoconductor drum 222 to an predetermined
electric potential; a developing device 224 for developing an
electrostatic latent image formed on the photoconductor drum 222
into a visible image by supplying toner to the electrostatic latent
image; a transfer device (transfer charger, etc.) 225 for
transferring a toner image formed on the surface of the
photoconductor drum 222 to a recording sheet; a cleaning device 226
for removing the remaining toner on the photoconductor drum 222
after the transfer of the toner image; and a discharging device
(discharger) 229 for removing electric charges from the
photoconductor drum 222 from which the toner image has been
transferred. The recording sheet to which toner image is
transferred is conveyed to the fixing unit 217 and toner image is
fixed to the recording sheet by heat pressing process.
There are provided in addition to the above mentioned fixing unit
217 at the discharge side of the image forming unit 210 a
switch-back path 221 for inverting a recording sheet upside down to
form an image on the back side of the recording sheet and a
post-processing unit 260 equipped with a up/down tray 261 for
stapling the recording sheet on which the image is formed. As
necessary, the recording sheet on which the toner image is fixed at
the fixing unit 217 is passed through the switch-back path 221,
conveyed to the post-processing unit 260 by the operation of a
discharge roller 219 where it is post-processed, and discharged
into the up/down tray 261.
A sheet feeding unit is provided beneath the image forming unit
210. The sheet feeding unit is composed of a hand-feed tray 254, a
both-side unit 255, and a sheet tray 251 provided in the body of
the digital multiple function printer 100, and a group of different
sheet trays 252 and 253 provided in a multi-tray feeder 270 which
can be separated from the digital multiple function printer 100. In
the body of the digital multiple function printer 100, a transfer
mechanism 250 is provided for transferring the recording sheets
from the trays 251, 252, 253 and 254 to a transfer position where a
transfer device 225 of the image forming unit 210 is located.
The both-side unit 255 is also communicated with the switch-back
path 221 for inverting the recording sheet upside down thus to form
images on both sides of the recording sheet. The both-side unit 255
may be replaced with a common sheet cassette. Also, a large volume
sheet tray for storing as a larger number of sheets as several
thousands may be provided as not shown.
The digital multiple function printer 100 shown in FIG. 11 includes
the control unit 41 as well as other functional blocks shown in
FIG. 9.
The operation of the digital multiple function printer 100 equipped
with the sheet feeding apparatus of the present invention will now
be described for one example procedure by the control unit 41
referring to the flowcharts of FIG. 12 and FIG. 13.
The control unit 41 determines by a detection result given from the
document tray lower-limit position detector S8 whether or not the
document tray 22 is at its lower-limit position when the digital
multiple function printer 100 is switched on and stays at the
standby state (Step S11). When the document tray 22 is not at the
lower-limit position (No at Step S11), the control unit 41 controls
the elevation/lowering motor 33 to lower the document tray 22 to
the lower-limit position (Step S12). At this time, the processes of
steps S11 and S12 are repeated until the document tray 22 comes at
the bottom of the front end into contact with the stopper 280 and
its contact is detected by the document tray lower-limit position
detector S8.
When the document tray 22 is at the lower-limit position (Yes at
Step S11), the control unit 41 holds the state (Step S13). More
specifically, when operation for lowering the document tray 22 is
executed, the control unit 41 stops the elevation/lowering motor 33
to stop lowering the document tray 22. When the document tray 22 is
already at the lower-limit position, the control unit 41 controls
no operation.
Next, the control unit 41 determines a detection result of the
lower document detector S1 (Step S14). When the detection result of
the lower document detector S1 is not at the detection (ON) state
but at the non-detection (OFF) state (No at Step S14), the control
unit 41 then determines a detection result of the upper document
detector S1' (Step S15). When the detection result of the upper
document detector S1' is not at the detection (ON) state but at the
non-detection (OFF) state (No at Step S15), the control unit 41
determines that no document is set on the document tray 22 and
returns the process to Step S11.
On the other hand, when the detection result of the upper document
detector S1' is at the detection (ON) state (Yes at Step S15), the
control unit 41 determines that the documents are not correctly set
on the document tray 22 and displays a guidance on the operation
panel P of the operation unit 46 for confirming the set condition
of the documents on the document tray 22 (Step S16). Then, the
control unit 41 returns the process to Step S11.
When it is judged "YES" at Step S14 described above, that is, the
detection result of the lower document detector S1 is at the
detection (ON) state, the control unit 41 then determines the
detection result of the upper document detector S1' (Step S17).
When it is determined that the detection result of the upper
document detector S1' is at the detection (ON) state (Yes at Step
S17), the control unit 41 determines from both the detection (ON)
states of the upper document detector S1' and the lower document
detector S1 that a sufficient number of documents are set on the
document tray 22 as shown in FIG. 6 where the presence of the
documents is successfully detected by not only the lower document
detector S1 but also the upper document detector S1'. In this case,
the control unit 41 reserves a relatively large area in the image
memory 40 for storage of the read data (Step S18). Simultaneously,
the control unit 41 inhibits any other processing requiring the use
in the image memory 40, for example, receiving of image data
transmitted from the external through the communication network
(Step S19).
On the other hand, when it is judged that the detection result of
the upper document detector S1' is at the non-detection (OFF) state
(No at Step S17), the control unit 41 determines from the detection
(ON) state of the lower document detector S1 that a smaller number
of documents are set on the document tray 22 as shown in FIG. 5
where the presence of documents is detected by only the lower
document detector S1. In this case, the control unit 41 reserves a
relatively small area in the image memory 40 for storage of the
read data (Step S20). Simultaneously, the control unit 41 permits
another processing requiring the use in the image memory 40, for
example, receiving image data from the external through the
communication network (Step S21).
When the process at Step S19 or S21 has been executed, the control
unit 41 starts elevation of the document tray 22 by controlling the
elevation/lowering motor 33 (Step S22) and determines a detection
state of the guide-in roller position detector S2 (Step S23). At
the beginning, the detection state of the guide-in roller position
detector S2 is non-detection state (OFF) (No at Step S23). As the
document tray 22 elevates and reaches at a position for pressing up
the guide-in roller R1 with the uppermost layer of the stack of the
documents, this state is detected (ON) by the guide-in roller
position detector S2 (Yes at Step S23). At this time, the control
unit 41 executes control for stopping the elevation/lowering motor
33 to stop the elevation of the document tray 22 (Step S24), and
once enters the standby state. Then, according to a start signal
generated by, for example, depressing the start key K5 on the
operation unit 46, the control unit 41 starts the feeding and
conveying documents and reads document images (Step S25).
Accordingly, in the procedure shown in the flowcharts of FIG. 12
and FIG. 13, based on the detection states of the lower document
detector S1 and the upper document detector S1', that is, each
detector detects or not that documents are set on the document tray
22, the control unit 41 can determine the state where the documents
are not correctly set, the state where a relatively large number of
documents are set, or the state where a relatively small number of
documents are set.
The control unit 41 then generates a warning when judging the state
where documents are not correctly set, and prepares for reserving a
relatively large area in the image memory 40 for storage of the
read data when judging the state where a relatively large number of
documents are set, or reserving a relatively small storage area in
the image memory 40 when judging the state where a relatively small
number of documents are set.
The storage capacity of the image memory 40 will now be explained
in brief. It is assumed that the image data of an A4 size document
is about 4 MB before subjected to compression. For storage of all
the data read from two hundreds of A3 size documents, the image
memory 40 has to store a storage area of substantially 1.6 GB. It
is assumed that the capacity of the image memory 40 is 1.6 GB, when
the control unit 41 judges at Step S17 that a smaller number or not
larger than 100 of the documents are set on the document tray 22
and the first and second document size detectors S0 and S7
determine that the size of the document sheets is A4, the image
memory 40 has to store a storage area of substantially 400 MB. It
is hence desired to provide a storage area of 512 MB of the image
memory 40 for storage of the read data. As the remaining storage
area in the image memory 40 is allocated for another external data
transmitted from the external through the communication network or
the like, the simultaneous processing operation can be
conducted.
Next, another example of the operation by the control unit 41 in
the digital multiple function printer 100 equipped with the sheet
feeding apparatus of the present invention will be explained
referring to the flowcharts of FIG. 14 and FIG. 15. The steps S31
to S37 in the flowcharts of FIG. 14 and FIG. 15 are identical to
the steps S11 to S17 in the flowcharts of FIG. 12 and FIG. 13 and
will be explained in no more detail. The procedure in the
flowcharts of FIG. 14 and FIG. 15 will be explained after it is
judged "YES" at Step S34 as the step S14 has determined "YES" in
the flowcharts of FIG. 12 and FIG. 13.
When it is judged "YES" at Step S34, that is, the detection result
of the lower document detector S1 is at the detection (ON) state,
the control unit 41 determines a detection result of the upper
document detector S1' (Step S37). When the detection result of the
upper document detector S1' is at the detection (ON) state (Yes at
Step S37), the control unit 41 judges that a relatively large
number of documents is set on the document tray 22, i.e., the
presence of documents is detected by not only the lower document
detector S1 but also the upper document detector S1' as shown in
FIG. 6. In this case, since the distance between the uppermost
layer of the stack of the documents set on the document tray 22 and
the guide-in roller R1 is relatively small, the control unit 41 set
the control condition of the elevation/lowering motor 33 for
elevating the document tray 22 at a speed set as a normal elevation
speed (Step S38).
On the other hand, when it is judged that the detection result of
the upper document detector S1' at Step S37 is at the non-detection
(OFF) state (No at Step S37), the control unit 41 determines from
only the detection result of the lower document detector S1 at the
detection (ON) state that a relatively small number of documents
are set on the document tray 22, i.e., the presence of documents is
detected by only the lower document detector S1 as shown in FIG. 5.
In this case, since the distance between the uppermost layer of the
stack of the documents set on the document tray 22 and the guide-in
roller R1 is relatively large, the control unit 41 set the control
condition of the elevation/lowering motor 33 for elevating the
document tray 22 at a higher speed than the speed set as the normal
elevation speed (Step S39).
The control unit 41 then controls the elevation/lowering motor 33
according to the elevation speed of the document tray 22 determined
by Step S38 or S39 (Step S40), and determines a detection state of
the guide-in roller position detector S2 (Step S41). At the
beginning, the detection state of the guide-in roller position
detector S2 is at the non-detection (OFF) state (No at Step S41).
As the document tray 22 elevates to push up the guide-in roller R1
with the uppermost layer of the stack of the documents, this state
is detected (ON) by the guide-in roller position detector S2 (Yes
at Step S41). At this time, the control unit 41 executes control
for stopping the elevation/lowering motor 33 to stop the elevation
of the document tray 22 (Step S42), and once enters the standby
state. Then, according to a start signal generated by, for example,
depressing the start key K5 on the operation unit 46, the control
unit 41 starts the feeding and conveying documents and reads
document images (Step S43).
Accordingly, in the procedure shown in the flowcharts of FIG. 14
and FIG. 15, based on the detection states of the lower document
detector S1 and the upper document detector S1', that is, each
detector detects or not that documents are set on the document tray
22, similar to the procedure shown in the flowcharts of FIG. 12 and
FIG. 13, the control unit 41 can determine the state where the
documents are not correctly set, the state where a relatively large
number of documents are set, or the state where a relatively small
number of documents are set.
In the procedure shown in FIG. 14 and FIG. 15, the control unit 41
generates a warning when judging the state where documents are not
correctly set, and sets the elevation speed of the document tray 22
to the normal speed when judging the state where relatively large
number of documents are set, or sets the elevation speed of the
same at higher than the normal speed when judging the state where
relatively small number of documents are set. This permits the
document tray 22 to be elevated at the higher speed throughout the
relatively large distance between the uppermost layer of the stack
of the documents and the guide-in roller R1 when the number of
documents set on the document tray 22 is relatively small. As the
document tray 22 is elevated at the higher speed, feeding and
conveying the documents can be quickly started.
FIG. 16A and FIG. 16B are graphic diagrams showing the control
states (the control states of the rotational speed) of the
elevation/lowering motor 33 at Steps S38 and S39 in the flowcharts
of FIG. 14 and FIG. 15. At the control for elevating the document
tray 22 at the normal elevation speed executed at Step S38, the
elevation/lowering motor 33 is rotated with a constant rate of 500
pps (pulses per second) from the time t1 to t2 as shown in FIG.
16B. The time t1 is the time when the control unit 41 judges at
Step S37 that the upper document detector S1' is at the detection
(ON) state. Similarly, the time t2 is the time when the control
unit 41 judges at Step S41 that the guide-in roller position
detector S2 is at the detection (ON) state.
On the other hand, at the control for elevating the document S36 as
shown in FIG. 16A, the elevation/lowering motor 33 is activated at
500 pps at the time t1 and increased its rotational speed up to
1500 pps and then becomes constant speed. Although not shown in the
flowcharts of FIG. 14 and FIG. 15, the rotational speed of the
elevation/lowering motor 33 begins to decrease its rotational speed
to 500 pps from the time t4 when the upper document detector S1' is
turned to the detection (ON) state, and then stops at the time t6
when the control unit 41 judges that the guide-in roller position
detector S2 is turned to the detection (ON) state.
While the procedure in the flowcharts of FIG. 12 and FIG. 13 and
the procedure in the flowcharts of FIG. 14 and FIG. 15 are
described separately for conducting different operations, they may
simultaneously be executed in a parallel processing mode.
As described above, according to the sheet feeding apparatus of the
present invention, the actuator (contact) of the sensor (detector)
for detecting a stack of the documents stored (set) on the document
tray 22 is separated into two parts and provided at both upper and
lower sides of the document tray 22. This can minimize the length
of both the actuators S1a and S1a'. Also, as any undesired sheet
which is curled upwardly is detected with the actuator S1a' of the
upper document detector S1', the detecting operation will generate
minimum error.
Further, according to the sheet feeding apparatus of the present
invention, the detecting areas of the two actuators S1a and S1a' of
the upper and lower document detectors S1 and S1' partially overlap
each other, thus creating no undetectable area. Also, since the
overlap area between the two detecting areas of the upper and lower
document detectors S1 and S1' is sufficiently increased, the
detecting operation can be stable regardless of any discrepancy in
the characteristics of the document detectors S1 and S1'.
Further, according to the sheet feeding apparatus of the present
invention, when number of the sheets stored on the document tray 22
increases, the control unit 41 controls the height of the uppermost
of the sheets stored on the document tray 22 to keep at a
predetermined height. Accordingly, the sheets can be fed out one by
one from the uppermost one, hence ensuring the stability of the
feeding operation. Also, as the document tray 22 is elevated or
lowered within the detecting areas of the two document detectors S1
and S1', the document sheets can certainly be detected for their
presence or absence regardless of the position of the document tray
22.
Further, according to the sheet feeding apparatus of the present
invention, the volume of the sheets stored in the document tray 22
is roughly determined by combining the two detection results of the
upper and lower document detectors S1 and S1'. More particularly,
it is judged that the number of the sheets is small when the upper
document detector S1' detects the presence of the sheets and the
lower document detector S1 detects the absence of the sheets in the
document tray 22. It is judged that the number of the sheets is
large when both the upper and lower document detectors S1' and S1
detect the presence of the sheets. It is hence judged that no sheet
is set in the document tray 22 when both the upper and lower
document detectors S1' and S1 detect the absence of the sheets.
Also, it is judged that the number of the sheets is small in the
document tray 22 positioned at upper when only the lower document
detector S1 detects the presence of the sheets. On the contrary, it
is judged that the number of the sheets is small in the document
tray 22 positioned at lower when only the upper document detector
S1' detects the presence of the sheets.
Further, according to the sheet feeding apparatus of the present
invention, the control unit 41 controls the elevation/lowering
motor 33 to elevate or lower the document tray 22 at a higher speed
to the corresponding position where the sheets can be picked up
from the document tray 22 when it is judged that the number of the
sheets is small in the document tray 22 located at its lower-limit
position where a maximum of the sheets can be loaded.
Also, the image reading apparatus of the present invention can
hence be realized featuring the advantages of the sheet feeding
apparatus described above.
Also, the image forming apparatus of the present invention can
hence be realized with the image reading apparatus featuring the
advantages of the sheet feeding apparatus described above.
Further, the image forming apparatus of the present invention can
hence be realized featuring the advantages of the image reading
apparatus equipped with the sheet feeding apparatus described
above.
Further, according to the image forming apparatus of the present
invention, the image memory 40 is arranged to use a minimum of its
storage campsite storing the data of images when the number of the
sheets stored in the document tray 22 is relatively small and thus
allocate the remaining storage area for other processing. This
allows the image reading operation of the image reading apparatus
to be conducted in parallel with another processing such as the
image forming process based on the image data received from a
peripheral device, hence improving the efficiency of the overall
operation.
In a conventional sheet feeding apparatus, for the purpose of
detecting a relatively large number of the sheets in the sheet
storing unit from a maximum to zero, a single contact provided for
contacting with the leading end of a sheet is required to increase
the length thereof. Also, when the contact is arranged to extend
from upper side to lower side of the sheet storing unit, as the
contact is rotatably moved for clearing each of the sheets being
fed out, its movement requires a considerable capacity in the
document storage. The length of the contact is hence limited
because the movement in the space interrupts any roller or its axis
of the feeding mechanism. Moreover, when the contact is arranged to
extend from lower side to upper side in the sheet storing unit, it
may hardly detect any upwardly curled sheet thus declining the
accuracy of the detection.
The sheet feeding apparatus of the present invention has two
contacts provided at both upper and lower sides of the sheet
storing unit. This allows the length of the contacts to be
shortened. Also, as any upwardly curled sheet is favorably be
detected by one of the contacts, the detecting operation will be
minimized in detection error.
The sheet feeding apparatus of the present invention has the
detecting areas of the two, first and second, contacts arranged to
partially overlap each other, thus creating no undetectable area
where either of the contacts cannot reach. Also, since the overlap
between the two detecting areas of the two contacts is sufficiently
increased, the detecting operation can be stable regardless of any
discrepancy in the characteristics of the two contacts.
The sheet feeding apparatus of the present invention is arranged in
which a stack of the sheets is controllably kept so that the
uppermost sheet is kept at the predetermined height when the number
of the sheets in the sheet storing unit is increased. Accordingly,
the sheets can be fed out one by one from the uppermost one, hence
ensuring the stability of the feeding operation. Also, as the sheet
storing unit is controlled to elevate and lower within the
detecting areas of the two, first and second, contacts, the sheets
can certainly be detected for their presence or absence regardless
of the position of the sheet storing unit.
The sheet feeding apparatus of the present invention permits the
volume of the sheets stored in the sheet storing unit to be roughly
determined by combining the detection result of the first contact
and the detection result of the second contact. More specifically,
it is judged that the number of the sheets is small when the first
contact detects the presence of the sheets and the second contact
detects the absence of the sheets. It is judged that the number of
the sheets is large when both the first and second contacts detect
the presence of the sheets. It is hence judged that no sheet is
stored when both the first and second contacts detect the absence
of the sheets. Also, it is judged that the number of the sheets is
small in the sheet storing unit positioned at upper when only the
second contact detects the presence of the sheets. On the contrary,
it is judged that the number of the sheets is small in the sheet
storing unit positioned at lower when only the first contact
detects the presence of the sheets.
The sheet feeding apparatus of the present invention is arranged in
which the motor is controlled for driving the elevation/lowering
mechanism of the sheet storing unit at a higher speed when it is
judged that the number of the sheets is small in the sheet storing
unit positioned at its lower-limit position where a maximum of the
sheets can be stored. As a result, the sheet storing unit can
quickly be elevated to the position where the sheets can be picked
up from the sheet storing unit.
The image reading apparatus of the present invention can hence be
provided featuring the advantages of the sheet feeding apparatus
described above.
The image forming apparatus of the present invention can hence be
provided featuring the advantages of the sheet feeding apparatus
described above.
The image forming apparatus of the present invention can hence be
provided featuring the advantages of the image reading apparatus
described above.
The image forming apparatus of the present invention has the memory
arranged to use a minimum of its storage capacity for storing the
data of images when the number of the sheets stored in the sheet
storing unit is relatively small and thus allocate the remaining
storage area for other processing. This allows the image reading
operation of the image reading apparatus to be conducted in
parallel with another processing such as the image forming process
based on the image data received from a peripheral device, hence
improving the efficiency of the overall operation.
As the present invention may be embodied in several forms without
departing from the spirit of essential characteristics thereof,
those embodiments are therefore illustrative and not restrictive,
since the scope of the present invention is defined by the appended
claims rather than by the description preceding them, and all
changes that fall within metes and bounds of the claims, or
equivalence of such metes and bounds thereof are therefore intended
to be embraced by the claims.
* * * * *